src/time/strftime.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <langinfo.h>
   5 #include <locale.h>
   6 #include <time.h>
   7 #include <limits.h>
   8 #include "locale_impl.h"
   9 #include "time_impl.h"
  10
  11 static int is_leap(int y)
  12 {
  13         /* Avoid overflow */
  14         if (y>INT_MAX-1900) y -= 2000;
  15         y += 1900;
  16         return !(y%4) && ((y%100) || !(y%400));
  17 }
  18
  19 static int week_num(const struct tm *tm)
  20 {
  21         int val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
  22         /* If 1 Jan is just 1-3 days past Monday,
  23          * the previous week is also in this year. */
  24         if ((tm->tm_wday + 371U - tm->tm_yday - 2) % 7 <= 2)
  25                 val++;
  26         if (!val) {
  27                 val = 52;
  28                 /* If 31 December of prev year a Thursday,
  29                  * or Friday of a leap year, then the
  30                  * prev year has 53 weeks. */
  31                 int dec31 = (tm->tm_wday + 7U - tm->tm_yday - 1) % 7;
  32                 if (dec31 == 4 || (dec31 == 5 && is_leap(tm->tm_year%400-1)))
  33                         val++;
  34         } else if (val == 53) {
  35                 /* If 1 January is not a Thursday, and not
  36                  * a Wednesday of a leap year, then this
  37                  * year has only 52 weeks. */
  38                 int jan1 = (tm->tm_wday + 371U - tm->tm_yday) % 7;
  39                 if (jan1 != 4 && (jan1 != 3 || !is_leap(tm->tm_year)))
  40                         val = 1;
  41         }
  42         return val;
  43 }
  44
  45 const char *__strftime_fmt_1(char (*s)[100], size_t *l, int f, const struct tm *tm, locale_t loc, int pad)
  46 {
  47         nl_item item;
  48         long long val;
  49         const char *fmt = "-";
  50         int width = 2, def_pad = '0';
  51
  52         switch (f) {
  53         case 'a':
  54                 if (tm->tm_wday > 6U) goto string;
  55                 item = ABDAY_1 + tm->tm_wday;
  56                 goto nl_strcat;
  57         case 'A':
  58                 if (tm->tm_wday > 6U) goto string;
  59                 item = DAY_1 + tm->tm_wday;
  60                 goto nl_strcat;
  61         case 'h':
  62         case 'b':
  63                 if (tm->tm_mon > 11U) goto string;
  64                 item = ABMON_1 + tm->tm_mon;
  65                 goto nl_strcat;
  66         case 'B':
  67                 if (tm->tm_mon > 11U) goto string;
  68                 item = MON_1 + tm->tm_mon;
  69                 goto nl_strcat;
  70         case 'c':
  71                 item = D_T_FMT;
  72                 goto nl_strftime;
  73         case 'C':
  74                 val = (1900LL+tm->tm_year) / 100;
  75                 goto number;
  76         case 'e':
  77                 def_pad = '_';
  78         case 'd':
  79                 val = tm->tm_mday;
  80                 goto number;
  81         case 'D':
  82                 fmt = "%m/%d/%y";
  83                 goto recu_strftime;
  84         case 'F':
  85                 fmt = "%Y-%m-%d";
  86                 goto recu_strftime;
  87         case 'g':
  88         case 'G':
  89                 val = tm->tm_year + 1900LL;
  90                 if (tm->tm_yday < 3 && week_num(tm) != 1) val--;
  91                 else if (tm->tm_yday > 360 && week_num(tm) == 1) val++;
  92                 if (f=='g') val %= 100;
  93                 else width = 4;
  94                 goto number;
  95         case 'H':
  96                 val = tm->tm_hour;
  97                 goto number;
  98         case 'I':
  99                 val = tm->tm_hour;
 100                 if (!val) val = 12;
 101                 else if (val > 12) val -= 12;
 102                 goto number;
 103         case 'j':
 104                 val = tm->tm_yday+1;
 105                 width = 3;
 106                 goto number;
 107         case 'm':
 108                 val = tm->tm_mon+1;
 109                 goto number;
 110         case 'M':
 111                 val = tm->tm_min;
 112                 goto number;
 113         case 'n':
 114                 *l = 1;
 115                 return "\n";
 116         case 'p':
 117                 item = tm->tm_hour >= 12 ? PM_STR : AM_STR;
 118                 goto nl_strcat;
 119         case 'r':
 120                 item = T_FMT_AMPM;
 121                 goto nl_strftime;
 122         case 'R':
 123                 fmt = "%H:%M";
 124                 goto recu_strftime;
 125         case 's':
 126                 val = __tm_to_secs(tm) - tm->__tm_gmtoff;
 127                 width = 1;
 128                 goto number;
 129         case 'S':
 130                 val = tm->tm_sec;
 131                 goto number;
 132         case 't':
 133                 *l = 1;
 134                 return "\t";
 135         case 'T':
 136                 fmt = "%H:%M:%S";
 137                 goto recu_strftime;
 138         case 'u':
 139                 val = tm->tm_wday ? tm->tm_wday : 7;
 140                 width = 1;
 141                 goto number;
 142         case 'U':
 143                 val = (tm->tm_yday + 7U - tm->tm_wday) / 7;
 144                 goto number;
 145         case 'W':
 146                 val = (tm->tm_yday + 7U - (tm->tm_wday+6U)%7) / 7;
 147                 goto number;
 148         case 'V':
 149                 val = week_num(tm);
 150                 goto number;
 151         case 'w':
 152                 val = tm->tm_wday;
 153                 width = 1;
 154                 goto number;
 155         case 'x':
 156                 item = D_FMT;
 157                 goto nl_strftime;
 158         case 'X':
 159                 item = T_FMT;
 160                 goto nl_strftime;
 161         case 'y':
 162                 val = (tm->tm_year + 1900LL) % 100;
 163                 if (val < 0) val = -val;
 164                 goto number;
 165         case 'Y':
 166                 val = tm->tm_year + 1900LL;
 167                 if (val >= 10000) {
 168                         *l = snprintf(*s, sizeof *s, "+%lld", val);
 169                         return *s;
 170                 }
 171                 width = 4;
 172                 goto number;
 173         case 'z':
 174                 if (tm->tm_isdst < 0) {
 175                         *l = 0;
 176                         return "";
 177                 }
 178                 *l = snprintf(*s, sizeof *s, "%+.4ld",
 179                         tm->__tm_gmtoff/3600*100 + tm->__tm_gmtoff%3600/60);
 180                 return *s;
 181         case 'Z':
 182                 if (tm->tm_isdst < 0) {
 183                         *l = 0;
 184                         return "";
 185                 }
 186                 fmt = __tm_to_tzname(tm);
 187                 goto string;
 188         case '%':
 189                 *l = 1;
 190                 return "%";
 191         default:
 192                 return 0;
 193         }
 194 number:
 195         switch (pad ? pad : def_pad) {
 196         case '-': *l = snprintf(*s, sizeof *s, "%lld", val); break;
 197         case '_': *l = snprintf(*s, sizeof *s, "%*lld", width, val); break;
 198         case '0':
 199         default:  *l = snprintf(*s, sizeof *s, "%0*lld", width, val); break;
 200         }
 201         return *s;
 202 nl_strcat:
 203         fmt = __nl_langinfo_l(item, loc);
 204 string:
 205         *l = strlen(fmt);
 206         return fmt;
 207 nl_strftime:
 208         fmt = __nl_langinfo_l(item, loc);
 209 recu_strftime:
 210         *l = __strftime_l(*s, sizeof *s, fmt, tm, loc);
 211         if (!*l) return 0;
 212         return *s;
 213 }
 214
 215 size_t __strftime_l(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm, locale_t loc)
 216 {
 217         size_t l, k;
 218         char buf[100];
 219         char *p;
 220         const char *t;
 221         int pad, plus;
 222         unsigned long width;
 223         for (l=0; l<n; f++) {
 224                 if (!*f) {
 225                         s[l] = 0;
 226                         return l;
 227                 }
 228                 if (*f != '%') {
 229                         s[l++] = *f;
 230                         continue;
 231                 }
 232                 f++;
 233                 pad = 0;
 234                 if (*f == '-' || *f == '_' || *f == '0') pad = *f++;
 235                 if ((plus = (*f == '+'))) f++;
 236                 width = strtoul(f, &p, 10);
 237                 if (*p == 'C' || *p == 'F' || *p == 'G' || *p == 'Y') {
 238                         if (!width && p!=f) width = 1;
 239                 } else {
 240                         width = 0;
 241                 }
 242                 f = p;
 243                 if (*f == 'E' || *f == 'O') f++;
 244                 t = __strftime_fmt_1(&buf, &k, *f, tm, loc, pad);
 245                 if (!t) break;
 246                 if (width) {
 247                         /* Trim off any sign and leading zeros, then
 248                          * count remaining digits to determine behavior
 249                          * for the + flag. */
 250                         if (*t=='+' || *t=='-') t++, k--;
 251                         for (; *t=='0' && t[1]-'0'<10U; t++, k--);
 252                         if (width < k) width = k;
 253                         size_t d;
 254                         for (d=0; t[d]-'0'<10U; d++);
 255                         if (tm->tm_year < -1900) {
 256                                 s[l++] = '-';
 257                                 width--;
 258                         } else if (plus && d+(width-k) >= (*p=='C'?3:5)) {
 259                                 s[l++] = '+';
 260                                 width--;
 261                         }
 262                         for (; width > k && l < n; width--)
 263                                 s[l++] = '0';
 264                 }
 265                 if (k > n-l) k = n-l;
 266                 memcpy(s+l, t, k);
 267                 l += k;
 268         }
 269         if (n) {
 270                 if (l==n) l=n-1;
 271                 s[l] = 0;
 272         }
 273         return 0;
 274 }
 275
 276 size_t strftime(char *restrict s, size_t n, const char *restrict f, const struct tm *restrict tm)
 277 {
 278         return __strftime_l(s, n, f, tm, CURRENT_LOCALE);
 279 }
 280
 281 weak_alias(__strftime_l, strftime_l);